/**
 * struct TreeNode {
 *  int val;
 *  struct TreeNode *left;
 *  struct TreeNode *right;
 *  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param root TreeNode类
     * @return int整型
     */
    int ret = -0x3f3f3f3f;
    int dfs(TreeNode* root) {
        if (root == nullptr)
            return 0;
        int left = max(0, dfs(root->left));
        int right = max(0, dfs(root->right));
        int cur = left + right + root->val;
        ret = max(ret, cur);
        // cout << "cur data: " << root->val << " -> " << cur << " ret:" << ret << endl;
 
        return max(0, max(left, right)) + root->val;
    }

    int maxPathSum(TreeNode* root) {
        dfs(root);
        return ret;
    }
};